Find the Largest Open Intervals Where the Function Is Concave $f(x)=x^{3}+3 x^{2}-9 x+5$

Multiple Choice

Find the largest open intervals where the function is concave upward.
- $f(x) =x^{3}+3 x^{2}-9 x+5$

A) None
B) $(-1, \infty) ,(-\infty,-1)$
C) $(-1, \infty)$
D) $(-\infty,-1)$